The structure of SAE system is illustrated in FIG. 1. The following is a description of the structure of the SAE system in FIG. 1.
101 User Equipment (UE) is a terminal device to receive data. 102 EUTRAN is a radio access network in the evolved system SAE, including a macro base station (eNB), which is responsible for providing a radio network access interface for LTE mobile phones, and is connected with the mobile management entity MME 103 and the user plane entity 104 Serving Gateway (S-GW) of the mobile phones through the interface S1 . 103 MME is responsible for managing UE's mobile context, session context, and saving user security information. 104 Serving Gateway primarily offers the functions in the user plane. The interface S1 -MME is responsible for establishing radio access bearer for UE, forwarding the messages sent from UE to MME through the radio access network. The combined function of 103 MME and 104 Serving Gateway is similar to that of the original 108 SGSN (General Packet Radio Service (GPRS) supporting node). And it is possible that both MME and Serving Gateway could locate at the same physical entity. 105 PDN Gateway (PDN GW) is responsible for functions such as charging and legal listening. Both the Serving Gateway and the PDN Gateway may locate at the same physical entity. 108 SGSN offers routing for data transmission in the existing UMTS. The existing SGSN finds corresponding Gateway GPRS Supporting Nodes (GGSN) according to a Access Point Name (APN). 109 HSS is a home subscription sub-system for subscribers, which is responsible for saving subscriber information, such as the UE's current location, the serving node's address, subscriber security information, UE's activated packet data protocol (PDP) context and so on. 106 PCRF offers QoS policy and charging rules through interface S7.
As shown in FIG. 2, the current HeNB system exists in 102 E-UTRAN. The current HeNB system has two possible architectures. One is that HeNB exists in E-UTRAN as a separate access equipment and the other is that two pieces of access equipment HeNB and HeNB GW exist in the E-UTRAN system. HeNB GW has less equipment and is used to manage a plurality of HeNBs. From the perspective of a core network, HeNB and HeNB GW can be regarded as the existing eNB, but the interface from HeNB GW or HeNB to the core network is the same as that of the existing SAE system. HeNB is deployed in a subscriber's home. If HeNB-GW exists in a HeNB system, it is deployed in the operator's network.
HeNB supports local route optimization function, including a direct access from UE to Internet through HeNB or a direct access from UE to other electronic equipments in the subscriber's home through HeNB, rather than through any core network node. This provides the advantage of reducing routing of subscriber data. When HeNB GW exists, the local route optimization function is still accessed to Internet through HeNB. There is no need to waste resources of the fixed network through HeNB GW.
In order to support the HeNB local route optimization function, the system architecture of the existing HeNB shall be enhanced. Since there are various possibilities, the architecture has not yet been finalized and only some basic principles are finalized, which include that HeNB needs to have the function of PDN GW (the PDN GW on HeNB, hereinafter referred to as PDN GWh for short). However, when the local route optimization service is activated, MME cannot correctly find a route to the PDN GW on HeNB according to the existing methods for finding PDN GW. Therefore, the present patent proposes an effective method for finding PDN GW.
In order to support the HeNB local route optimization function, there are several possibilities as follows:
Possibility 1: the HeNB network entity needs to have functions of Serving GW and PDN GW. When UE activates any other non-local route optimization service, it is necessary for the user plane routing requiring this service to pass through the Serving GW of the core network, rather than the Serving GW on HeNB while passing through the core network equipment. In such circumstances, there are two Serving GWs for the same UE network;
Possibility 2: the HeNB network entity has functions of Serving GW and PDN GW and when UE needs to activate any other non-local route optimization service, it is necessary for the user plane routing requiring this service to pass through the Serving GW on HeNB while passing through the core network equipment.
Possibility 3: the HeNB network entity has functions of Serving GW, PDN GW and MME. In this case, when the local route optimization service is activated, it is unnecessary for a signaling of the control plane to go to MME of the operator's network. In the circumstances, it not only saves the data routing of the user plane but also saves the signaling of the control plane.